Heretofore, as a top coat for automobile bodies and the like, there have been used coating compositions based essentially on amino alkyd resin, amino acrylic resin or the like. However, in the former, though the application characteristics and finishing appearance (gloss, glamorous) are comparatively good, there is the problem of inferior weather resistance, whereas in the latter, although the weather resistance is excellent, there remain questions of inferior finishing appearance, impact resistance and the like.
On the other hand, oil-free polyester/aminoaldehyde resin type coating compositions have been believed to be hardly applicable as top coat was for automobile bodies and the like, because the compositions have difficulties in being applied onto automobile bodies due to the generation of fish eyes, and also exhibit inferior gloss and poor compatibility with amino resins or the like, irrespective of various advantages, such as excellent weather resistance, mechanical properties, inaterlaminar adhesion, and the like.
Poor pigment dispersibility has also been a big factor in keeping such resins from actual use in coating areas.
Recently, various attempts have been made on the oil-free polyester/amino formaldehyde resin type coating composition to make the most of the advantages and overcome the drawbacks possessed by them, thereby making it possible to apply these resins as a top coat for automobile bodies and the like. Among them, particular attention has been concentrated upon saturated alicyclic acid modified polyester resin consisting essentially of oil-free polyesters to which particular amounts of saturated alicyclic polycarboxylic acids are included as an acid component thereof. (see Japanese Patent Application Nos. 94269/79 and 111062/80).
While the abovementioned modified polyester/aminoaldehyde resin type coating composition may give improved weather resistance and some improvements in such respect to overcoming the drawbacks by the heretofore known oil-free polyester compositions such as the generation of fish eyes and poor compatibility with amino resins, it is hardly possible to say that the abovementioned drawbacks have been thoroughly overcome in that there still remains the question of inferior pigment dispersibility and insufficient curability due to the modification of these resins with alicyclic acid. Therefore, such compositions had not come into practical use.
An object of the invention is, therefore, to provide a polyester base resinous composition for coating use having the merits of heretofore known oil-free polyester/amino resin type coating composition and being free of all of the demerits of using such modified polyester resins as mentioned above.